Rotary reamers are used while drilling to enlarge the diameter of a borehole. When rotating, the reamers may have axes perpendicular or parallel to the tubular.
PCT application no. PCT/CA2010/000697 discloses a downhole tool for selectively reaming a wellbore or stabilizing drill string components within a wellbore which includes an elongate tool body adapted to receive reamer cartridges or stabilizer cartridges. The cartridges have a reamer insert with an array of cutting elements. The reamer insert rotates about a rotational axis transverse to the longitudinal axis of the tool.
The Halliburton Corporation also manufactures a near bit reamer tool that may be used behind the drill bit or further up the bottomhole assembly (BHA) in rotary steerable systems. Backreaming cutters mounted on pistons allow rotation out of the hole if the BHA gets stuck. The reamer is provided on a separate sub that may be inserted in the drill string.
It is useful for a reamer to be close to the bottom of the string to reduce flex and drift. In the cited cases, the downhole tool is a separate tool that is attached along the drill string. The upper and lower ends of the tools are adapted to other drill string components.